Had a loud squeak noise coming from the rear of my truck for the longest time. Especially when driving over little bumps or undulations in the road. I checked many things, sway bar links, truck bed bolts, etc to no avail.

One day while waxing the truck I noticed if I pushed on the bed-side near the fuel filler door I could make the squeak happen at will!

I thought it was the fuel filler door assembly, so I removed it and cleaned things up around the edge of the fuel filler hole on the side of the truck bed.

And thats when I noticed the fuel filler neck was fairly loose in there. Turns out there is a clamp that is supposed to hold the fuel filler neck in place, and mine was no longer holding the fuel filler neck to the frame:



There is a tab on the top side that you can't see, that you slip the clamp over to hold the fuel filler neck in place. Mine wasn't holding anything, it had slipped off or something, and was allowing the fuel filler neck to rub against the frame causing the squeak.

I moved the clamp in place, tightened it down real good, and the truck is super quiet!

Maybe this will help someone else trying to track down a pesky squeak.